Starship Asterisk*

This artist's conception illustrates a supermassive black hole (central black dot) at the core of a young, star-rich galaxy. Now astronomers have found a rogue SMBH travelling through space. Image credit: NASA/JPL-Caltech

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Supermassive black holes (SMBHs) lurk in the center of large galaxies like ours. From their commanding position in the galaxy’s heart, they feed on gas, dust, stars, and anything else that strays too close, growing more massive as time passes. But in rare circumstances, an SMBH can be forced out of its position and hurtle through space as a rogue SMBH.

In a new paper, researchers from Canada, Australia, and the USA present evidence of a rogue SMBH that’s tearing through space and interacting with the circumgalactic medium (CGM). Along the way, the giant is creating shock waves and triggering star formation. ...

If you’ve never heard of a runaway SMBH, you’re not alone. SMBHs are normally locked into place at the centers of galaxies, and that’s where they stay. But scientists think that in rare circumstances SMBHs can escape their galaxies. In their paper, the authors explain how an SMBH can be cast out of its host galaxy.

It always starts when galaxies merge. That leads to the formation of a binary SMBH at the center of the merger remnant. The binary SMBH can be very long-lived, surviving for as long as one billion years before merging. If during that time, a third SMBH reaches the galactic center, then a three-body interaction can give one of the SMBHs a velocity boost, and it can be driven from the galaxy. ...

• arXiv > astro-ph > arXiv:2302.04888 > 09 Feb 2023